The present invention relates to an ink-jet printhead and a method for producing the same, and more particularly to a laminated ink-jet printhead provided with a piezoelectric actuator and a method for producing the same.
U.S. patent application Publication Ser. No. U.S. 2001/0,020,968 A1 discloses an on demand type ink-jet printhead provided with a piezoelectric actuator. The ink-jet printhead disclosed in the above mentioned publication includes a multi-layer cavity unit that has a plurality of nozzles and a plurality of pressure chambers being in fluid communication with respective ones of the nozzles. The pressure chambers are formed in the uppermost layer of the cavity unit with the upper sides thereof being opened.
The piezoelectric actuator is fixed on the top surface of the cavity unit so as to close or seal the upper sides of the pressure chambers. The piezoelectric actuator includes a plurality of active portions. Each active portions can selectively press one of the pressure chambers to eject ink filled therein through the corresponding nozzle.
The piezoelectric actuator is produced by laminating a plurality of rectangular green sheets and sintering the same. The sintered piezoelectric actuator is then placed on the top surface of the cavity unit with an adhesive layer therebetween and pressed against the cavity unit to be fixed thereon.
The four corners of the rectangular green sheets, however, often become warped in the thickness direction of the green sheets during the sintering process. FIG. 1A schematically shows an example of such sintered green sheets, or piezoelectric actuator 2, having warped corners. As shown in FIG. 1B, such warped corners cause a gap to be formed between the cavity unit 1 and the piezoelectric actuator 2 fixed thereon, which gap may cause a leak of ink from the pressure chambers. Further, the piezoelectric actuator 2 may break at the warped corners when it is pressed against the cavity unit 1 to be fixed on it.
U.S. Pat. No. 5,956,059 discloses an ink-jet printhead including a channel forming member made of ceramic sheets. Ceramic green sheets formed with cavities are stacked and sintered without any adhesive layers to produce a channel forming member having a plurality of pressure generating chambers and a common ink chamber.
Then, green sheets of piezoelectric material are adhered onto the top surface of the channel forming member to correspond to the respective pressure generating chambers, and sintered together with the channel forming member. With this, piezoelectric vibration plates are formed on the top surface of the channel forming member.
It should be noted that, the channel forming member has high mechanical strength at the time of the second sintering process for forming the piezoelectric vibration plates thereon since the channel forming member has been already sintered in advance of the second sintering process. Therefore, the channel forming member hardly warps as a whole during the second sintering process due to the shrinkage of the piezoelectric vibration plates.
In the above-mentioned ink-jet printhead, however, the rectangular ceramic sheets constituting the channel forming member shrink every time these sheets are sintered, once for forming the channel forming member and once for forming the piezoelectric vibration plates. Such repeated shrinkage of the ceramic sheets causes the corners thereof to become considerably warped.
Thus, there is a need for an ink-jet printhead by which the above mentioned problems do not arise.